Two Harvard University researchers said in a study published Wednesday they had collected scientific data proving Exxon Mobil Corp made "explicit factual misrepresentations" in newspaper ads it purchased to convey its views on the oil industry and climate science.

A significant body of investigative reporting has already shown that Exxon — along with other fossil fuel companies — has long been aware of the causes, consequences, and facts related to human-caused climate change. Harvard researchers Geoffrey Supran and Naomi Oreskes have gone a step further by demonstrating that Exxon acknowledged the reality of climate change in academic papers and internal documents while promoting doubt in public-facing communications.

In an article published in the journal Environmental Research Letters, Supran and Oreskes said they examined 187 documents, including internal memos, peer-reviewed papers by Exxon scientists and New York Times "advertorials" that Exxon paid to have published in the style of opinion pieces. The researchers said they used a social science analysis method to turn statements in the documents into data points that could be counted and compared.

The authors wrote: "Accounting for expressions of reasonable doubt, 83% of peer-reviewed papers and 80% of internal documents acknowledge that climate change is real and human-caused, yet only 12% of advertorials do so, with 81% instead expressing doubt. We conclude that ExxonMobil contributed to advancing climate science — by way of its scientists' academic publications — but promoted doubt about it in advertorials."

The controversy about Exxon's promotion of public doubt about global warming has plagued Secretary of State Rex Tillerson, the former CEO of ExxonMobil. Tillerson has refused to answer questions about whether Exxon intentionally lied to the public and shareholders about the dangers of climate change.

The Harvard researchers wrote that their analysis of the documents makes the answer to that question clear.

"Given this discrepancy, we conclude that ExxonMobil misled the public," they said.

Tillerson may one day be forced to testify about the matter under oath, since New York Attorney General Eric Schneiderman is currently investigating whether ExxonMobil misled investors about the impact of climate change. According to the Associated Press, Schneiderman's office has said the investigation already uncovered “Exxon’s significant potential investor fraud.”

The investigation also forced Exxon to acknowledge that Tillerson used the alias “Wayne Tracker” in some internal Exxon email communications